(a) Field of the Invention
This invention relates to a light-source cover for controlling transmission of light from a light source mounted in a portable device and a portable device with the same.
(b) Description of the Related Art
Photography in dark places uses at flash. It is desirable in such a case that the photo is taken, without adverse effects from the flash, with naturalness as if taken in the daylight. Therefore, a light-source cover is placed in front of the light source to diffuse light.
Mobile phones employ a simple light source, such as an LED, owing to size constraint. In taking a photo in the dark, the light source is switched on to provide a clear picture image. The light source is used also as a spot light for shining on the user's hand in the dark. Furthermore, when a call or a mail is incoming, the light source blinks to let the user know it. The light source is covered with a light-source cover on which an opalescent medium print is made to reduce light transmission and into which a light diffusion agent is mixed to provide a light diffusion effect and a blinder effect.
Cameras, such as a single-lens reflex camera, generally use an electronic flash in taking photos in the darkness. For example, Published Japanese Patent Application No. H10-39377 discloses an electronic flash in which a light controller placed in front of an umbrella reflector is composed of a diffusion control part having a light diffusion effect on light from a stroboscopic tube only in the longitudinal direction of the tube and a collection control part having a light collection effect of collecting incident light to all the directions. Thus, the light controller can diffuse incident light from the stroboscopic tube in the longitudinal direction of the stroboscopic tube at the diffusion control part. This provides a variable irradiation angle electronic flash limiting the prism effect of the light controller.
Published Japanese Patent Application No. H10-68987 discloses an optical material placed in front of a bar-like light source and composed of first and second collection lenses located on the right and left sides, respectively, of a reference line orthogonal to the longitudinal direction of the bar-like light source. The first and second collection lenses have an optical property of hardly diffusing light from the light source in the direction of the reference line but largely diffusing the light in the longitudinal direction of the light source. This provides an optical material and an electronic flash with the same which largely diffuse light from the light source particularly in the longitudinal direction of the light source and thereby enable setting of a light distribution characteristic of having a wide light irradiation angle.
Published Japanese Patent Application No. 2004-138784 discloses an electronic flash in which a light controller placed in front of a bar-like light source includes a diffusion control part formed in one surface of the light controller and collection control parts formed at lateral ends of the light controller not corresponding to the aperture of an umbrella reflector in wide angle mode. The diffusion control part has a light diffusion effect on light from the bar-like light source only in the longitudinal direction of the bar-like light source. One of the collection control parts has a light collection effect on light from the bar-like light source only in the longitudinal direction of the bar-like light source. The other collection control part has a light collection effect on light from the bar-like light source only in the direction orthogonal to the longitudinal direction of the bar-like light source.
The conventional light-source cover having a medium print, however, considerably reduces the illuminance and, therefore, the light source often does not act well as a fill light for photography. In other words, if greater importance is given to the appearance, the illuminance becomes poor.
For mobile phones, the locations of their light-source covers and light sources are limited. Therefore, mobile phones have constraints, such as the impossibility of stacking two light-source covers and the impossibility of using a light source capable of emitting a powerful flash, unlike conventional electronic flashes.